Surge protector



Oct. 5, 1965 A. c. DEMURJIAN 3,210,588

SURGE PROTECTOR Filed May 22, 1962 INVENTOR. ASHOD CHARLES DEMURJIAN ATTORNZ United States Patent M 3,210,588 SURGE PROTECTOR Ashod Charles Demurjian, Cranston, RJ.

(53 John St., Cumberland, RI.) Filed May 22, 19,62, Ser. No. 196,737 Claims, (Cl. 313-311) My present invention relates to the electrical art and more particularly to an arc discharge device used to protect electrical and electronic circuits.

The principal object of the present invention is to provide a device for protecting electrical components from excessive voltage surges.

Another object of the present invention is to provide a protective device in the form of an arc discharge device which will recover after breakdown and automatically operate on the next surge voltage.

A further object of the present invention is to provide an arc discharge device in which the arc trap elements are easily replaceable without disturbing the circuit.

A further object of the present invention is to provide an arc trap device which is simple in construction and easy and economical to manufacture and assemble.

With the above and other objects and advantageous features in view my invention consists of a novel arrangement of parts more fully disclosed in the detailed description following in conjunction with the accompanying drawings and more particularly defined in the appended claims.

In the drawings,

FIG. 1 is a perspective view of .a surge voltage protecting device embodying my invention.

FIG. 2 is a longitudinal section thereof taken on line 22 on FIG. 1.

FIG. 3 is a perspective view of the replaceable arc trap element.

There are many types of electrical and electronic components and equipment which require protection from voltage surges such as lightning which might damage expensive equipment. Typical equipment requiring such protection are power supplies, transformers, rectifiers, electronic tubes, telephones, outdoor lighting fixtures, etc. The device of the present invention is an arc discharge device having two terminal elements connected from the input terminal to the ground thus shunting the voltage surge through the ground and away from the equipment being protected. The usual method is to provide a fusing element which melts and produces a short circuit when broken down by the voltage surge. It is then necessary to replace the element in order to operate the electrical component. The present invention is designed to provide an arc trap in the form of an arc gap between two electrodes. The breakdown voltage rating is determined by the dimensions of the air gap between the terminals. When the voltage exceeds .the set rating there is a breakdown resulting in a spark across the gap. Since the heat of the sparking and the exchange of materials caused by the spark surge normally destroys the exact setting of the gap, this too must be replaced.

The present invention therefore provides an arc gap made of special materials which do not distort, are not affected by the heat of the spark and are therefore automatically recoverable and ready to operate on the next voltage surge. To separate two materials and produce a spark gap in the lower voltage ranges and with a fine rating, it is necessary that the material used have certain properties. First of all it must have an extremely high melting point beyond the foreseeable heat range. Secondly, it must be of a very hard material capable of being polished to provide an accurate gap surface. The material must have good electrical and thermoconductivity and must be chemically inert to corrosion. Applicant Patented Oct. 5, 1965 has found that titanium diborate meets the above specifications. Molybdenum will also meet most of the specifications. However, applicant prefers the use of titanium dibor-ate. To protect against a low voltage surge, it is essential that the spark gap be small. Such small gaps are not accurate unless the surface is absolutely smooth and highly polished. Furthermore, after the first surge has caused a spark, the material must retain its surface characteristics so that the element will be ready for the next surge. 'For example a device set to operate at 200 v. should be able to breakdown at 250 v. to properly protect the equipment.

Referring more in detail to the drawings, it is contemplated that the arc trap elements be housed in a removable housing easy to replace if necessary, whereas the electrical connections can be made in a standard housing permanently attached. For example, viewing FIGS. 1 and 2, the housing 10 may be provided with external threads as illustrated for insertion into an electronic component, or may be made smooth and otherwise attached. The housing 10 is provided with a solid front end 11 to which an angular electrical conductive strip 12 is attached. The strip 12 is mounted on a dielectric disc which forms the front end 11 and the electrical conductive rivet 13 extends into the housing 10 as shown in FIG. 2. In electrical contact with the inner end of the rivet 13 is a spring 14 and disc or washer 15. The trap elements are housed in a plug 16 shown in FIG. 3 which is adapted to be inserted into the housing 10 and threaded thereto by means of threads 17.

The plug 16 comprises a cylindrical metal portion 18 having a ceramic insulator lining 19. At the forward end of the port-ion 18 is a positive anode 20 comprising a disc of titanium diborate or molybdenum having a highly polished flat surface 21. Spaced from the surface 21 is the cathode comprising a stick of carbon 22 also having a flat polished surface 23 opposing the surface 21. The gap 24 between the surfaces 21 and 23 controls the ca pacity of the device. By positioning the surfaces 21 and 23 close to each other so that the gap 24 is extremely narrow, small low voltage surges will cause sparking and grounding. Different cartridges can therefore be supplied with different spark gaps for different ratings. It is not necessary to hermetically seal the item but it can be sealed if desired.

The above described device will not break down under repeated surges and is automatically reset for the next surge of voltage. Thus if there is a line surge causing a spark and grounding of the current, the current can immediately continue to flow to the device without the necessity of replacing the plug 16. This self-healing property is the result of the construction used and is what distinguishes the present invention from the devices now in use.

'If desired a carbon cathode can also be replaced by a cathode made of titanium diborate. This produces two finely polished surfaces. Other advantages of the present invention will be readily apparent to a person skilled in the art.

I claim:

1. A surge protector for an electrical circuit comprising a housing, a cathode mounted in said housing, an anode mounted in said housing spaced from said cathode, said mountings forming a predetermined spacing forming a spark gap for grounding a surge in an electric line above a predetermined maximum, said anode comprising titanium diborate.

2. A surge protector for an electrical circuit comprising a housing, a cathode mounted in said housing, an anode mounted in said housing spaced from said cathode, said mountings forming a predetermined spacing forming a spark gap for grounding a surge in an electric line above a predetermined maximum, the opposed surfaces of said -mountings forming a predetermined spacing forming a spark gap for grounding a surge in an electric line above a predetermined maximum, the opposed surfaces of said anode and cathode being polished, fiat, parallel surfaces,

'saidfcathode comprising a bar of carbon, said anode comprising titanium diborate.

4. A surge protector for an electrical circuit comprising a housing, a cathode mounted in said housing, an anode mounted in said housing spaced from said cathode, said mountings forming a predetermined spacing forming a spark gap for grounding a surge in an electric line above a predetermined maximum, the opposed surfaces of said anode and cathode being polished, flat, parallel surfaces, said cathode comprising a bar of carbon, said anode comprising titanium diborate, and a base having the electrical connections for the electrical circuit, said housing forming a replaceable cartridge adapted to be inserted into said base.

5. A surge protector for an electrical circuit comprising a housing, a cathode mounted in said housing, an anode mounted in said housing spaced from said cathode, said mountings forming a predetermined spacing forming a spark gap for grounding a surge in an electric line above a predetermined maximum, the opposed surfaces of said anode and cathode being polished, fiat, parallel surfaces,

said anode and cathode comprising titanium diborate.

References Cited by the Examiner UNITED STATES PATENTS 2,619,518 11/52 'Kelsay 200-115 X 3,102,968 9/63 Waterton 313-311 DAVID J. GALVIN, Primary Examiner. 

5. A SURGE PROTECTOR FOR AN ELECTRICAL CIRCUIT COMPRISING A HOUSING, A CATHODE MOUNTED IN SAID HOUSING, AN ANODE MOUNTED IN SAID HOUSING SPACED FROM SAID CATHODE, SAID MOUNTINGS FORMING A PREDETERMINED SPACING FORMING A SPARK GAP FOR GROUNDING A SURGE IN AN ELECTRIC LINE ABOVE A PREDETERMINED MAXIMUM, THE OPPOSED SURFACES OF SAID ANODE AND CATHODE BEING POLISHED, FLAT, PARALLEL SURFACES, SAID ANODE AND CATHODE COMPRISING TITANIUM DIBORATE. 